This paper investigates the extent to which the timeliness of UK private companies' accounting information reflects regulatory and economic influences by studying the impact of a one month shortening of the statutory regulatory filing deadline. Using the financial reporting lag and propensity to file late as measures of timeliness, we find that although reporting behaviour is largely driven by regulatory deadlines, companies conjectured to be producing accounting information for reporting to outside investors publish their accounts significantly more quickly, and are substantially less likely to file beyond the statutory deadline (late), than their counterparts lacking similar incentives. However, in terms of this reporting lag differential, the change in regulation had a homogeneous impact. We report a significant reduction in the mean and median filing time, but an increase of 46% in the proportion of firms filing late, in the year following the regulatory change. Our results are robust to the employment of a number of different estimation methods, including matching and Huber and median regression.