Definition
A spousal RRSP allows the higher-income spouse to contribute to an RRSP registered in the lower-income spouse's name. The contributing spouse deducts the contribution using their own RRSP contribution room, reducing their current-year tax. When the spousal plan is eventually drawn down, income is taxed in the annuitant spouse's hands - typically at a lower marginal rate in retirement. The income-splitting benefit is subject to the spousal RRSP attribution rule under ITA s.146(8.3): if the annuitant spouse withdraws funds from the spousal RRSP in the same calendar year as a spousal contribution was made, or in either of the two preceding calendar years, the amount withdrawn is attributed back to the contributing spouse and taxed in their hands, up to the amount of contributions made in that three-year window. Contributions made before the three-year window are not attributed. Spousal RRSPs must be converted to a RRIF by December 31 of the year the annuitant spouse turns 71.
Source
Income Tax Act s.146(8.3); CRA T4040 (RRSPs and Other Registered Plans)