Why Do House Bills Start At 4001?

(Source: MIRS.news, Published 10/17/2025) It’s been two weeks of the House not holding session after passing the state budget. And with no new legislative action in the lower chamber and a record low number of Public Acts signed this year, MIRS wanted to answer the question on everyone’s mind: Why do House bills start at HB 4001?

Every odd-numbered year, regardless of whether the Senate is starting a new term or not, both the House and Senate wipe clean the slate of bills introduced by the previous Legislature. The Senate begins with Senate Bill 1 and the House begins with House Bill 4001.

For the 103rd Legislature, HB 4001 was introduced by Rep. John Roth (R-Interlochen) to preserve Michigan’s tipped wage structure, and SB 1 was introduced by Sen. Jeremy Moss (D-Bloomfield Twp.) to apply the Freedom of Information Act (FOIA) to the Legislature and Governor’s office.

The collection of bills compiled by the Library of Michigan dates to 1861, when both House bills and Senate bills started at 1. The part-time Legislature met every other year in odd-numbered years, and both chambers’ bill numbers ran concurrently until 1953, when the Senate began starting their bill numbers at 1001 and the House went on starting at 1.

Senate bills beginning at 1001 and House bills beginning at 1 continued from 1953 through 1964, when the number of House bills got up to 958, and there were fewer than 50 bills left to introduce in the special session that year before bills would have the same number again.

Then in the 1965-66 session, the first of what became Michigan's full-time Legislature under the 1963 Michigan Constitution, Senate bills went back to starting at 1, and House bills began at 2001. That practice only lasted a few sessions until the 1971-72 session, when 4001 became the first House bill for each session.

The mechanics of the 1964 election were chaotic due to a Supreme Court ruling that state Senate districts (and House Districts) had to equate to one-person, one vote as opposed to Senate districts that were based on geography.

Michigan became the first state to redistrict its Legislature since the court's historic one-man, one-vote decision. For more on that, MIRS wrote an eight-part series in 2019 about it.

This brought an enormous change in the state Legislature, said former House Speaker Bobby Crim, then 34, one of the new faces swept into the Legislature at that time. He said roughly half of the House was brand new. They had new energy and new ideas, which brought about a lot of new bills. In the 1965-66 session, the House introduced 1,931 bills and the Senate introduced 1,238.

Prior to that, each chamber averaged around 400 bills per session.

With the start of that session, the Legislature ended its part-time Legislature format and went to full time, meaning there would be more bills since sessions spanned two years instead of one. While he doesn't have a direct memory of this being the case, Crim said it would only make sense that the bill sequence coming out of the chamber was changed to reduce confusion for everyone involved.

"The bills had to be a high enough number to not be confused with the bills in the other chamber," he said. "It's really the only explanation. Honestly, I never thought much about it because I never considered it important. What the hell is the difference?"

Prior to 1965-66, he said a legislative session would see a few hundred bills per chamber per session. After 1965-66, this was multiplied manyfold, requiring more Legislative Service Bureau staff to handle the requests and the bill drafting.

From 1965-1970, House bills started at 2001. In those three sessions, there were 1,931, 2,231 and 2,899 bills introduced, with the bill numbers being HB 3931 of 1966, HB 4231 of 1968 and HB 4899 of 1970. Meanwhile, in the upper chamber, the number of bills introduced was approaching 2,001. In 1970, there were 1,783 Senate bills introduced, leaving around 200 bills of cushion before bill numbers overlapped.

Former House staffer Bruce Timmons said he remembers that after the 1969-70 session, the decision was made with the clerical staff and LSB that House bills would start at 4001 given that the Senate was only 218 bills away from hitting 2001 by session prior. As with a few sessions prior, there was concern about overlap of bills and confusion.

Crim said he doesn't remember this switch because “what difference did it make?" However, he said the explanation tracks because “bushels and bushels of bills were being introduced” at that time in Michigan history.

So, House bills started at HB 4001 in that 1971 session, and it has stayed that way ever since.