Tax Day is less than a month away. If you haven’t met with an accountant by now, you might be out of luck.

Tax professionals are starting their days early and staying late to do as much as they can before the April 15 deadline, and many are booked and hustling to finish returns for existing customers, says Troy Lewis, head of the tax executive committee for the American Institute of CPAs. That means new customers may not get an appointment until after the filing season has passed, he says.

“For the most part, if folks haven’t met with the accountant or started the process themselves,” Lewis says, “they may find themselves short on help.”

While this year’s tax season started a bit earlier, that head-start has done little to ease the typical crunch in late March and early April, Lewis says. A few hiccups delayed important paperwork and has forced taxpayers to wait to finish their returns.

For instance, some had to wait longer than usual for 1099 forms this year, Lewis says. And some who bought insurance on the public health exchanges last year were asked to hold off filing returns after they received 1095-a forms with incorrect information. All the while, the April 15 deadline for filing — and paying — taxes hasn’t budged.

That doesn’t account for the most common issue contributing to a last-minute surge in tax return filings: procrastination. About half of taxpayers say they’ve requested an extension for their tax returns at some point, according to a Jackson Hewitt survey. The most popular reason for needing more time, cited by 16 percent of people, was that the deadline “just snuck up” on them.

Still, accountants aren’t necessarily turning everyone away, Lewis says. Many pros are happy to help taxpayers file for an extension so that they can get more time to finish their returns and then make an appointment for preparing those returns after the crush has past. Some accountants may also help people estimate how much they owe.

Taxpayers who are running behind should get started by handing their tax pros the documents they have, even if they don’t have everything they need to complete their returns. “It’s far easier for a professional to insert two additional pieces of information on April 3 than to start the entire process,” Lewis said.

If they still don’t think they’ll finish their returns on time, they should file form 4868 to request an automatic six-month extension for filing their returns, says Mark Steber, chief tax officer for Jackson Hewitt. That would eliminate late filing penalties on taxes owed, which are steeper than late payment penalties, he says.

Finally, Steber says, they should pay what they can by the deadline and try to work out a payment plan with the IRS for the rest.