The Internal Revenue Service ruled yesterday that banks and savings and loan associations may continue to offer package deals linking high interest rate bonuses with tax-free All Savers certificates, provided the link is optional.

That means customers must be given the choice of either having the money they invested in the high-interest repurchase agreements automatically rolled over into an All Savers account or withdrawing their money and the accrued interest before Oct. 1 without penalty. Customers involved in any program that does not offer that option would lose the tax exemption for the All Savers certificate.

The rate on All Savers certificates to be sold starting Oct. 1 is 12.61 percent. The interest rate, which is tied to the monthly auction of one-year Treasury notes, will change at the first of each month for new certificates.

While the IRS was ruling on tax status of the new plans, federal financial regulators yesterday ruled that banks and savings institutions could offer the All Savers certificates in any denomination or increment they wanted. But all institutions will be required to offer $500 certificates, the one denomination spelled out by Congress in the new tax law. Regulators also ruled depositors would lose three months' interest for early withdrawal, as well as forfeit the tax exemption on the entire certificate.

Interest on All Savers accounts is not subject to state tax in Maryland or Virginia. The interest is subject to District of Columbia tax.

The IRS action represents a compromise from its warning last weekend that depositors might lose their tax exemptions by participating in the advertised plans offering bonus interest on All Savers certificates.

The weekend warning and yesterday's ruling were caused by newspaper advertisements offering up to 50 percent annual interest rates to persons signing up in advance to buy tax free All Savers certificates which go on sale Oct. 1. It is expected that between $120 billion and $250 billion will be deposited in these accounts over the next 15 months.

The IRS warned that the bonus interest payment would push the entire yield and the maturity on a certificate over those permitted by Congress. And if a certificate does not conform to the law, it does not qualify for a tax exemption. The advertisements initially caused confusion among readers who did not realize the high rates lasted only until Oct. 1. Then the IRS warning caused confusion among financial institutions, some of which withdrew their offers.

IRS commissioner Roscoe L. Egger Jr. said at a press conference yesterday that his agency had not ruled on the question sooner because the advertisements did not begin appearing in Washington papers until late last week, although they had appeared at least a week before that in other parts of the country. Moreover, no financial institution called the IRS to check the legality of the bonus offer.

In an attempt to rule on the multitude of deals offered, the IRS signed off on nine different situations and said that all others would be decided case by case.

The customer can get a tax exemption in the following cases: when the purchase is made Oct. 1; when the purchase is made before Oct. 1 and both buyer and seller agree that the buyer can "elect without penalty to have his funds remitted on Oct. 1 or reinvested on that date." (If the customer elects to have his funds reinvested on Oct. 1, that constitutes two separate transactions, so the tax exemption on the certificate is upheld. The bonus interest is, of course, taxable.)

The customer can also get a tax exemption even if a premium of minimal value, such as a toaster, is given for opening the account, or if he rolls over a money market certificate before maturity.

The customer cannot get a tax exemption if "the repurchase agreement (repo) interest rate is linked to All Savers election, if reinvestment is automatic, if there is a special option for future repo purchase, if there is a simultaneous linked purchase of repo and All Savers, or if loan discounts are linked to All Savers."

In other words, financial institutions may urge customers to commit their funds in advance in exchange for a bonus, but they must make clear in writing there is no obligation on the customer's part to buy an All Savers certificate in order to get the bonus. Moreover, the customer is not obliged to say in advance if he will pull his money out before Oct. 1. He may, however, accept the bonus without tax consequences if he desires. If he does, he should keep the written notice provided by the seller as proof the package deal conformed to the law just in case the IRS audits his return and questions the tax exemption on interest.

It was unclear yesterday how many banks and thrifts would continue to offer high interest repos between now and Oct. 1 in the knowledge that customers could withdraw their funds before that date. Egger said he assumed most would "decouple" their offers, but it has no power to make them do so. First Women's Bank of Maryland said it would offer customers the standard repo rate of 15-16 percent, but not a bonus rate.

As for persons who have already bought package deals, the IRS had mixed news. Egger said financial institutions were obligated to notify them in writing of the situation. The IRS does not have the power to "grandfather" existing accounts, or make an exception for those taxpayers who have already bought non-conforming package deals. In this instance the customer must deal directly with the financial institution to make the package conform to the law.