IT IS NO SECRET that politicians depend on contributions for all sorts of expenses, from campaigns to constituent services -- and D.C. Council member Charlene Drew Jarvis is no exception. But when it comes to timely reporting of who gave what and when -- which is an important requirement of the law -- the city's campaign finance office says Mrs. Jarvis does seem to be an exception: though all her council colleagues who have such funds appear to have filed their reports properly, campaign finance director Keith A. Vance says Mrs. Jarvis has not filed finance records on her constituent fund for five years. Mr. Vance says the discovery was made in the wake of his notifying Mrs. Jarvis a year ago that she had failed to file seven overdue campaign-contribution reports.

Woodrow Boggs, chairman of her 1982 and 1984 campaigns, first said that private accountants were reviewing records for her campaign-contribution and constituent-service funds and that a report would be forthcoming a week ago Monday. Meanwhile, Mrs. Jarvis says she did not receive Mr. Vance's request for a reply by Oct. 4 until last Wednesday. Yesterday she requested an extension until Oct. 17 to provide for a complete review by a certified public accountant she has retained.

Mrs. Jarvis says her recollection is that she filed the reports and says she is perplexed by the apparent absence of filings. No one is charging that any funds were misspent or that there were any other violations of campaign regulations. But this matter should be pursued until some answers are found. Public disclosure is an essential element of the political system. It is also the law here.